Background TIM-3 and CD39 are co-expressed in tumor-infiltrating T cells and antigen-presenting cells and considered to act as negative regulators of anti-tumor immunity. TIM-3 has multiple ligands including galectin-9, phosphatidylserine, CEACAM-1 and HMGB1. Although galectin-9 induces apoptosis in T cells via TIM-3, most of the TIM-3 antibodies under clinical development only partially block the galectin-9-binding to TIM-3. Adenosine is an immunosuppressive metabolite that suppresses T and NK cells. Inhibition of ATP-hydrolysis by purinergic ectoenzyme CD39 may recover anti-tumor immunity through reducing adenosine level in tumor microenvironment. We report herein BP1210, a novel TIM-3 biparatopic antibody (BpAb), that blocks the binding of multiple ligands including galectin-9 and BP1212, a bispecific antibody (BsAb) against TIM-3 and CD39, that blocks TIM-3-signaling and adenosine-mediated immune suppression.
Methods The antibodies against TIM-3 and CD39 were cloned from mice immunized with recombinant proteins. Optimal combinations of clones were selected by functional assay for BpAb and BsAb, then the CDRs were grafted to human framework in effector null scFv-Fc format with knobs-into-holes mutations. Binding affinities and blocking/inhibiting activities were analyzed using recombinant proteins and cells endogenously expressing TIM-3 or CD39. The proliferation and cytokine production of T cells induced by antibodies were determined using human peripheral blood mononuclear cells (PBMCs). Anti-tumor efficacy of BP1210 was investigated in tumor models in huTIM-3 knock-in mice or in NOG mice transplanted with PBMCs.
Results BP1210 BpAb that fully blocks the interaction of TIM-3 to both galectin-9 and phosphatidylserine, enhanced the activation of T cells stimulated by the antigen. i.e., BP1210 increased the population of IFNγ+ T cells, the production of cytokines, and suppressed the apoptosis of T cells, which are higher than other TIM-3 antibodies that fully blocks the binding to phosphatidylserine but not to galectin-9. in vivo studies showed that BP1210 retards the tumor growth and enhances the tumor-growth suppression by anti-PD-L1 antibody. BP1212 BsAb preferentially bound to the CD39+TIM-3+ cells (exhausted T cells and APCs) and effectively blocked the enzymic activity of CD39 and binding to TIM-3 ligands in these cells. BP1212 augmented the proliferation and cytokine production of T cells, suggesting that BP1212 enhances the T cell immunity even in immunosuppressive tumor microenvironment.
Conclusions BP1210 and BP1212 show the advantages over conventional TIM-3 and CD39 antibodies in T cell-mediated tumor immunity. Our engineered antibodies with novel combinations of antibody clones against immune checkpoints will provide new therapeutic options of tumor immunotherapy.
Ethics Approval The present study was approved by the Institutional Ethics Committee of BrightPath Biotherapeutics Co., Ltd.(approved number: ERD-01). Animal studies were approved by the Institutional Animal Care and Use Committee (approved number: 22012A and 22014A).
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